Here is the full list of all 35 Boss Crushers achievements.
Open any item or spell in the talent window
Reach the 1st boss
Reach the 2nd boss
Play in multiplayer
Kill the boss Zulgronn
Kill the boss Aoszru
Kill the boss Ananchi
Kill the boss Hastur
Kill 100 enemies
Kill 500 enemies
Spend HP on a random box
Complete 8 rooms without getting damage
Clean out 25 rooms
Clean out 100 rooms
Find 10 books of spells
Pick up 20 healing runes
Reach level 10 guild
Reach level 20 guild
Kill the boss and get 5 stars
Kill 20 mobs with one hit
Kill the boss MG300P
Kill the boss Destroyer 17
Reach the 3nd boss
Complete level Fire Hammer
Complete level Dark mines
Complete level Edge of reality
Complete level Hive
Complete level Treasure house
Complete level Tomb
Kill the boss Zulgronn on maximum difficulty
Kill the boss Aoszru on maximum difficulty
Kill the boss Hastur on maximum difficulty
Kill the boss Ananshi on maximum difficulty
Kill the boss MG300P on maximum difficulty
Kill the boss Destroyer 17 on maximum difficulty